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Low-power wireless stand-alone sensors that can operate without any wiring have received significant attention in sensor network applications. These devices harvest environmental energy resources to supply their power and transfer their collected data using wireless RF links. In many instances, the power supplied from the environment is far less than the power required by the sensor device. In this case, the main solution is to accumulate energy on a storage element, and when enough energy is stored, the sensor node is instantaneously activated using an undervoltage lockout (UVLO) circuit. During this short time burst, the sensor performs the required acquisition, transmits the results, and enters a sleep mode until again enough energy is collected. The quiescent current of the UVLO is the main factor that determines the minimum power level at which the sensor node is still operational. Most wake-up circuits used in conventional devices suffer from a quiescent current of a few hundred nanoamperes. In this article, using a zero-bias-current MOSFET-based approach, a new wake-up circuitry is presented, which lowers the quiescent current down to the picoampere range. As a practical application, the effectiveness of the proposed circuit is shown in the soil moisture monitoring sensor setup.

Considering the characteristics of CMOS circuits that are susceptible to radiation, a stacked parallel CMOS transistor structure using 3.3V core MOSFET instead of 5V core MOSFET and a PMOS-controlled undervoltage lockout circuit are proposed. By thinning the gate oxide layer and using PMOS to control the comparison circuit technology, the locked voltage of the circuit after irradiation is almost unchanged and the leakage current is halved. On the basis of these structures, a half-bridge GaN gate driver is designed, which can realize the function correctly under irradiation, and even improve the power characteristics.

This paper focuses on a robust 10 kV SiC MOSFET gate driver with an improved desaturation protection scheme for overcurrent protection. The gate driver is designed for 10 kV/20 A SiC MOSFETs in a modular multilevel converter (MMC) submodule. The gate driver has short circuit protection, status feedback in every switching cycle, dead time insertion, and undervoltage lockout (UVLO) function to support robust continuous operation of the MOSFET and converter. Practical design considerations are elaborated to achieve these functions. With a digital blanking time of 600 ns, the improved desat protection achieves a response time of

A variable drive strength gate driver for gallium nitride (GaN) power FETs intended for a 6.6 kW EV charger is presented. The driver incorporates low-side and high-side channels in a single integrated circuit that is flip-chip capable. The gate driver has been designed in a 0.18 μm silicon-on-insulator (SOI) process featuring deep trench isolation, 1.8 V and 5 V CMOS devices, and DMOS devices rated up to 200 V. The on-chip protection circuitry includes an undervoltage lockout (UVLO) in both channels, desaturation detection, and a V DS sensing circuit for the low-side power FET. The novel V DS sensing implementation enables the gate driver to have a dynamically controlled source current, programmable between 0.15 A and 2.4 A, to mitigate excessive ringing. Both low and high-side channels have a sink current of 5 A. The gate driver IC also includes active Miller clamping, a low-side to high-side level shifter, and a power supply for each channel.

This paper presents the analysis and design of a current mode buck converter whose output voltage is set by a digital potentiometer programmed through an inter-integrated-circuit interface (PC). This converter can handle up to 300W output power, it has an input voltage of 48V and the output voltage ranging from 1. 5V up to 40 V with a mmimum output current of 7.5A.This converter has a high voltage, high efficiency, fixed frequency controller with programmable soft start, undervoltage lockout, current limit unaffected by duty cycle and internal high voltage regulator for its gate driver.This CMC buck converter was designed to be integrated in a computer controlled unit for electronic devices characterization (CCUEDC) [4] as an upgrade of the internal hysteretic buck converter. It can be also integrated in a highly efficient and versatile lab power supply or to be used to power LEDs devices.

We demonstrate the key module of comparators in GaN ICs, based on resistor-transistor logic (RTL) on E-mode wafers in this work. The fundamental inverters in the comparator consist of a p-GaN gate HEMT and a 2DEG resistor as the load. The function of the RTL comparators is finally verified by a undervoltage lockout (UVLO) circuit. The compatibility of this circuit with the current p-GaN technology paves the way for integrating logic ICs together with the power devices.

The paper is about the development of low power Low Dropout (LDO) regulator with additional housekeeping blocks including the Thermal Shutdown (TSD) and Undervoltage Lockout (UVLO) circuits as a temperature and voltage protection schemes for WSN application. The design is implemented using Synopsys Custom Designer tool, and the layout is physically verified using Hercules. The maximum power dissipation of the system is 298uW, with current efficiency of 76.77%.

In order to improve the stability of the GaN FET power driven integrated circuit, the integrated circuits usually design corresponding protective circuit modules, such as overcurrent, over temperature, under-voltage protection circuit, etc. In this paper, combined with the characteristics of GaN FET, based on the 0.18 m BiCMOS technique, a novel UVLO circuit used in GaN FET power driven integrated circuits is designed. The average temperature drift of turn on circuit voltage threshold(VDDTH+) is 0.12V, the maximum temperature drift is 0.481V, the average temperature drift of turn off threshold voltage(VDDTH-) is 0.03V, the maximum temperature drift is 0.142V; the VDDTH+ and VDDTH-are 4.241v and 3.885v; The hysteresis voltage is 356mv between VDDTH+ and VDDTH-, improved the circuit anti interference ability. The simulation results show that the circuit can output low voltage logic signals in under-voltage, and has low temperature drift and voltage hysteresis function, which has important significance for improving the performance of GaN FET power drive integrated circuit.

This paper proposes fluorescent electronic ballast with high power factor and low line input current harmonics. The system performance can be improved by a charged pump circuit. Details of design and circuit operation are described. The proposed electronic ballast is modified from single - stage half bridge class D electronic ballast by adding capacitor parallel with each power switch and setting the circuit parameter to operate under class DE inverter condition. By using this proposed method the DC bus voltage can be reduced around by 50% compare with conventional class D inverter circuit. Because the power switches are operated at zero voltage switching condition and low dv/dt of class DE switching. The experimental results show that the proper frequency of the prototype is around 50 kHz with input power factor of 0.982, THDi 10.2% at full load and efficiency of more than 90%.

The number of mobile device users increases every year. Each mobile device is usually equipped with a Li-ion battery having voltage that varies from a minimum of 2.7V to a maximum of 4.2V. Therefore, as the battery voltage decreases with time, a DC-DC converter is required for a regulated supply lower or higher than the battery voltage. A simple buck converter is not suited for this case, since step-up conversion is not available [1]. Instead, a non-inverting buck-boost converter can be a solution over the entire range of the battery voltage [1–4]. Many research studies related to buck-boost converters operated on Li-ion batteries set the target output voltage at around 3.4V [3,4]. Since Li-ion batteries have a wide plateau from 3.6V to 3.8V and a small energy storage below the plateau, DC-DC converters are generally operated on step-down mode at most of the battery voltage range, as shown in Fig. 10.4.1 top. Notwithstanding, step-up conversion is also required for extracting the energy below the plateau even if it is a small amount in the battery. Therefore, in DC-DC converters, it is critical to maintain high efficiency over the whole range of the battery voltage when it operates on both step-down and step-up modes to prolong the battery usage effectively. However, if the conventional buck-boost topology of Fig. 10.4.1 bottom-left is used for step-up and step-down purposes, there are always two switches (S 1 and S 3 ) conducting in the main current path through the inductor. Thus, the switches become large in size to minimize the conduction loss. As the switching loss also increases when the switch size is larger, the efficiency of this structure is usually lower than that of the simple buck (or boost) converter [1]. In this respect, this paper proposes a topology named a flying-capacitor buck-boost (FCBB) converter suitable for such an application by obtaining both step-up and step-down operations with high efficiency throughout the whole range of the battery voltage.

Recently, Li-ion battery is regarded as a potential energy storage device in the lime light and it can supply power to the satellite very effectively during eclipse. Because it has better features as high voltage range, large capacity and small volume than any other battery. Generally, multi cells are connected in series to use Li-ion batteries in satellite application. Since the internal resistance of cells is different each other, voltage in some cells can be overcharged or undercharged, so capacity of the cell is reduced and the life of whole battery pack is decreased. Therefore, a voltage balancing circuit with Fly-back converter is proposed and the voltage equalization of each cell is verified the prototype in this paper.

In the EV/HEV motor driving system, one of the most important elements that should be taken into account would be a battery that drives the whole system, because the rest of the circuit elements except battery have been relatively well established in the power electronics area. Because of the high frequency power harmonic noises inherent in the circuit, exact voltage fluctuation analysis of the driving circuit at the design stage has been emphasized quite a lot so far. This paper describes the analysis of motor driving circuit with novel battery model employed: as a result, the fluctuated battery voltage for a given DOD (Depth of Discharge) could be calculated. A filter design procedure that takes into consideration of the battery characteristics is also described for a fixed DOD. The effectiveness of the designed filter was confirmed by simulation, which was performed by using MATLAB, Ansys' Simplorer, and Agilent Technology's ADS (Advanced Design System). EV (Electric Vehicle) or HEV (Hybrid-Electric Vehicle) basically employs power electronic circuit to charge battery as well as to drive a motor, and the high voltage in the circuit, typically in the range of hundreds volts, needs to be chopped to control the driving circuits, and as a result it is inevitable to produce high frequency harmonic voltage/ current components inside. Therefore one of the most important things the HEV motor circuit designer needs to consider is the prediction of the electromagnetic compatibility of the driving circuit at the design stage. This is crucial to avoid unnecessary trial and errors after fabrication of the whole driving circuit only to find that the circuit needs to be revised to satisfy EMC standards such as IEC/CISPR and ISO. Therefore, precise analysis of the motor driving circuit is mandatory in the EV/HEV development process at the design stage. The main elements of power electronic circuit in the HEV are such as a high voltage battery, IGBT (Insulated Gate Bipolar Transistor) inverter to control motor through PWM (Pulse Width Modulation) algorithm, BLDC (Brushless DC) motor, and so on. Since the other elements except the battery have been common in the classical driving circuit simulation, an emphasis is put on the battery circuit modeling, which enables to simulate the driving circuit at various DOD levels. For this purpose, battery circuit model includes not only a simple DC model in time domain, but also complex R-C elements in frequency domain, coming from charge transfer resistance and double layer capacitors in the battery. Since the R and C in the battery model depend on the DOD level of the battery, one needs to take into consideration the frequency-dependent battery impedance as well as the load condition to design the filters in the motor driving circuit. (1)(2) This paper is organized as follows. In the next chapter, battery model which is used in the analysis of motor driving system is introduced. In chapter 3 all the circuit elements, such as battery, inverter, and filters, are integrated to form the whole circuit, and brief filter design procedure is described. Chapter 4 demonstrates the simulated results of the voltage fluctuations and the conducted noise, and the effectiveness of the filter is also shown. Finally, this paper ends with a conclusion and further works in the last section.

Has done research on the voltage of the battery management system to avoid the phenomenon of deep charging. The phenomenon of deep charging is a situation where the over current in the process of charging the battery because the battery voltage is below the allowed minimum voltage levels, this course can shorten the life of the battery or even permanently damage the battery. To prevent this, it is a regulatory system that serves to regulate the use of electric current to the battery, so when battery voltage is approach the level minimum, so electric current flowing from the battery to the load is automatically disconnected. The working principle of the system is to use a comparative setting, where these systems will compare the desired voltage as the voltage of the signal, with the other insert voltage as a reference. When all requirements are met comparators, then the outcome of the comparison system will measured increase in the voltage that will make a switch transistor saturation. To increase the switching currents, then used a relay that placed the series between the collector and voltage sources. Regulatory system is designed using components easily available in the market, and has the same functionality as the functions contained in the Battery Control Unit (CBU) Keywords - deep charging, over current, comparator, voltage reference

This paper presents the positive feed-forward control (PFFC) scheme associated with the average current-mode control (ACMC) scheme for the distributed power conversion system with the multiple voltage sources of different power ratings to protect individual voltage sources from the chain reaction of the undervoltage lockout in order not to cause system voltage collapse. The ACMC scheme has the inherent function of the negative feed-forward control (NFFC) to increase the input current of the converter by increasing the control duty cycle of the converter while the source voltage decreases. However, the undervoltage lockout protection of the employed source or converter can be activated if the source voltage drops below the set threshold value. Therefore, the PFFC+ACMC scheme is proposed to reduce the control duty cycle of the employed converter once the source voltage is less than the set threshold value to avoid system voltage collapse. The input current of the individual converter module is regulated by the proposed PFFC+ACMC mechanism in correspondence with the level of the sensed input terminal voltage. Finally, the prototype circuit of a simple interleaved buck-type converter system is built to validate the proposed PFFC+ACMC function.

The main functions of the Power Control and Distribution Unit (PCDU) in FORMOSAT-5 satellite are to condition energy from the solar arrays and distribute power for all subsystems on the satellite. The Power Relay (PR) module, one of the major modules in the PCDU is to manage the switchover of redundant DC-DC converter sections, secondary power distribution and power protections. The PR module controls power protections which are under voltage (UV) protection and Undervoltage-Lockout (UVLO) detection. UVLO detection monitors primary power voltage with majority voting in PR FPGA. UV detector switches nominal DC-DC converter to redundant DC-DC section, when under voltage happens. Power protection circuits all can be realized by Inverting Bistable Multivibrator. This paper describes protection methods for power and the reliable circuit design implementation.

In this paper describes the process of designing a protection circuit against an open or short electronic ballast. An open electronic ballast creates high voltages in a regular period, which a lies voltage stress on switching devices. On the other hand, a shorted output generates excessive current, causing problems such as heat generation in the ballast and reduced lifespan of semiconductor devices. This study proposes a protection circuit consisting of TTL and passive devices to resolve the problems. The proposed protection circuit offers the benefits of low cost and high reliability. The proposed circuit was connected to an actual ballast to demonstrate its applicability.

In this study, the system was designed for monitoring the voltage condition of each battery’s cell. The method used in this study is by using passive shunt resistor balancing method. An electronic circuit was designed in order to balance the value of the able voltage at the battery cells using resistors and then to remove the excess voltage. The result showed that the electrical circuit was capable to balance the voltage of each cell. Based on experiment with several values of load, it is can concluded that 0.1C rate of discharge has the best performance, because it does not affect battery voltage characteristic significantly which leads to better sensor reads.

CMOS under-voltage lockout (UVLO) circuit configured Schmitt trigger was fabricated and tested. The UVLO circuit consist of current source inverter, Schmitt trigger, delay circuit, and waveform shaper of the output. The tested result shows that the UVLO has size of die was 136 μm × 85 μm, turn on and off voltage was at 1.85V and 1.70V, respectively. The fabrication process was Magna/Hynix CMOS 0.35 μm process and supply voltage was 3.3V. Power dissipation of the UVLO was 0.18mW.

The role of the electric switch has two aspects: the first is the function of the switch itself. It is the tube and off of electric circuit and short circuit or over current that can be automatically jump to cut off the power supply and it has the effect of protection circuit and electric equipment. The second is the social function that people in today's life can not be lack. It can give people's work, study and life convenient, also can provide insurance coefficient. Thus, once it has quality problems, it will directly affect the quality of people's lives. Generally, the control class of low voltage electrical equipment mainly includes control relay and starter and other electrical equipment, power distribution type of low voltage electrical equipment mainly includes circuit breaker and switch control. Against such a situation, this article will focus on the performance analysis and design of low voltage electrical switch contact.

For stacked battery monitoring IC high speed and high precision voltage acquisition requirements, this paper introduces a kind of symmetrical type high voltage switch circuit. This kind of switch circuit uses the voltage following structure, which eliminates the leakage path of input signals. At the same time, this circuit adopts a high speed charge pump structure, in any case the input signal voltage is higher than the supply voltage, it can fast and accurately turn on high voltage MOS devices, and convert the battery voltage to an analog to digital converter. The proposed high voltage full symmetry switch has been implemented in a 0.18μm BCD process; simulated and measured results show that the proposed switch can always work properly regardless of the polarity of the voltage difference between the input signal ports and an input signal higher than the power supply.

This paper presents a design of high precision voltage measurement IP core for aware battery management SoC which is the key chip of Battery Management System (BMS) in electric vehicles. To meet the battery voltage detection requirements of high precision, synchronization and speed, a voltage detecting circuit which collects voltage of each battery cell precisely and synchronously is presented. To verify the circuit, a BMS test system is designed and built based on PCB. The test results show that the BMS based on the cell voltage measurement design presented in this paper can detect all cell voltages of the battery pack precisely with a maximum error of ±6mV, and synchronization is also considered. The relative measurement error is less than 0.2%. This IP core can be integrated in battery management SoC.

The paper presents a Li-ion Battery protect chip and the system combined with the actual commercial products. By giving a complete global view diagram, the paper introduces the implementation of several modules of the chip, including the voltage comparator circuit, the delay circuit and battery status monitor circuit. Battery status monitor circuit is responsible for monitoring the status of the battery, including over-current, short-circuit and charger detection. In addition, the circuit trimming technology is provided in brief introduction in the paper.

In designing interface circuits to a battery, often the battery is assumed to be a simple voltage source. However, the battery itself has internal parameters. This means that the internal parameters of the battery models need to be considered for the interface design. Several electrical battery models are presented. Then, using these electrical battery models, the analysis and the design of the interface circuit are described. Analysis and experimental results show that an electrical battery model which reflects battery characteristics has to be used for the optimal design of the interface circuit. Finally, the analysis results indicate that the required size of the condenser filter can be smaller with battery power supplies than with other power supplies, such as bridge-type AC source DC power supplies.

This paper presents the design and performance of an electronic ballast which provides a constant light output for wide input voltage fluctuations from 85V to 265V. Two IC's have been used in the design: the first part has a PFC controller IC and the second part IC is a ballast driver. The PFC circuit produces and maintains a constant power factor and a constant voltage of 400 V. The second part, the ballast driver IC feeds voltage to a resonant half bridge inverter operating in Zero Voltage Switching (ZVS) resonant mode, thereby reducing switching losses and the electromagnetic interference. The output to this part is constant light for the specified voltage range. Experimental results of the electronic ballast driving 36W fluorescent lamps are presented in order to confirm the feasibility of the performed design methodology.

A wide range of electronic equipment uses Uninterruptible Power System units in order to continue operating in case there is loss of power supply. Due to their battery, the Uninterruptible Power Systems guarantee that the electronic device will operate autonomously for a certain period of time. In this work, an automatic charger/regulator circuit for a lead- acid battery is developed. The charger/regulator circuit consists of the battery charger, the electronic circuit that supplies the load with DC voltage and the circuit that protects the battery from deep discharge. The specifications of the aforementioned circuit are appropriate for the DC voltage supply of a pharos's lighting device (fluorescent lamps). The charger/regulator circuit charges the battery via the 230V AC mains voltage in order to supply the lighting device (load) with 12V DC. In case the mains voltage is interrupted, the battery continues to supply the load with 12V DC. The battery stops to supply the load when its voltage becomes less than 9.5V, in order to avoid damage due to deep discharge. (5 pages)

This paper describes a simple architecture and low power consumption undervoltage lockout (UVLO) circuit with hysteretic threshold. The UVLO circuit monitors the supply voltage and determines whether or not the supply voltage satisfies a predetermined condition. The under voltage lockout circuit is designed based on CSMC 0.5um CMOS technology, utilizing a relatively few amount of circuitry. It is realized with a current source inverter. The threshold voltage is determined by the W/L ratio of current source inverter and resistor in reference generator. The hysteresis is realized by using a feedback circuit to overcome the bad disturbance and noise rejection of the single threshold. Hysteretic threshold range is 40mV. The quiescent current is about 1uA at 3V supply voltage,while the power of circuit consumes only 3uW.

In this paper, a sepic-type single-stage electronic ballast (STSSEB) is proposed. The ballast system can not only achieve high power factor but can reduce voltage stress, improve efficiency and lower cost. Since component stress is reduced significantly, the presented ballast can be applied to high input voltage system. Derivation of the STSSEB is first presented and analysis, design and practical consideration for the STSSEB are then presented. A 347Vac 60W prototype has been simulated and implemented. Simulations and experimental results have verified the feasibility of the proposed STSSEB.

This paper presents a method of merging the threshold voltage of zero temperature coefficients and comparative function into a single circuit. With application to undervoltage lockout circuit, it can reduce temperature sensitivity of threshold voltage and improve accuracy of threshold. Meanwhile, this undervoltage protection circuit realizes hysteretic threshold by a feedback control method so as to overcome disadvantage of poor interference rejection capability of single threshold. This undervoltage lockout circuit can be applied to DC-DC converter.

Optimizing energy consumption of a portable system directly affects the discharge current drawn from the battery. Since battery life ends when the battery voltage drops below a certain cutoff value, modeling the voltage-current relationship is important to system designers evaluating the impact of various design alternatives on the battery life. This paper presents a model that can accurately predict the battery voltage given current over time. Modeled phenomena include battery capacity loss at high discharge rates, charge recovery, and capacity fade with time.

This paper presents a simple alternative of electronic ballast operating in self-sustained oscillating mode with possibility of universal input voltage (90 V-240 V) supplying fluorescent lamps. The proximally constant lamp power is obtained by changing the resonant filter gain through frequency modulation in according to the input voltage. A voltage divisor supplies a control signal from the bus voltage to a control circuit. Thus, this additional circuit interprets the bus voltage value, controlling the self-oscillating gate-driver circuit switching frequency. Experimental results from one 40 W fluorescent lamp are presented to demonstrate the performance and the feasibility of the proposed system.

A reconfigurable high-speed switching regulator controller integrated circuit for power supply applications is introduced. The integrated circuit, designated as the FB3480, is an analog array chip with several preoptimized functional blocks usually found in high-performance controllers. In addition the chip has several large sections that can be reconfigured to meet specific design needs. The FB3480 contains a high-speed error amplifier with a bandwidth >4 MHz, a precision bandgap voltage reference (1%), a precision high-speed oscillator of frequency f>1 MHz, dual totem-pole output stages with an output >1.5 A, undervoltage lockout, high-speed ECL/EFL logic, and many uncommitted components for circuit customization. The discussion covers the FB3480 along with two of its derivatives, the ML4825 and the LM4809. >

A single lithium-ion battery protection circuit with high reliability and low power consumption is proposed. The protection circuit has high reliability because the voltage and current of the battery are controlled in a safe range. The protection circuit can immediately activate a protective function when the voltage and current of the battery are beyond the safe range. In order to reduce the circuit's power consumption, a sleep state control circuit is developed. Additionally, the output frequency of the ring oscillation can be adjusted continuously and precisely by the charging capacitors and the constant-current source. The proposed protection circuit is fabricated in a 0.5 μ m mixed-signal CMOS process. The measured reference voltage is 1.19 V, the overvoltage is 4.2 V and the undervoltage is 2.2 V. The total power is about 9 μ W.

A battery protection circuit for protecting a battery is proposed. The circuit includes a detecting circuit for detecting a battery condition and producing a detected voltage in relation to the battery condition, a comparator comparing the detected voltage with a given voltage, and a switching circuit controlling a connection between the battery and electrical elements. In the battery protection circuit, when the comparator determines that the battery needs to be protected from the battery condition, the switching circuit turns off to disconnect the battery from the electrical elements.

In communication equipment which uses a battery as the power supply, when a controller increases the transmission power at a transmitter corresponding to a drop in the electric field intensity, the controller lowers, accompanying that operation, a reference voltage from a reference voltage source which is used for comparison with the battery voltage for the purpose of detecting a drop in the battery capacity. Therefore, even when the battery voltage is dropped due to an increase in the transmission output, the reference voltage is also lowered correspondingly, so that there will not occur an erroneous detection of drop in the battery capacity due to the drop in the battery voltage.

A battery cell having a positive terminal, a negative terminal and a power producing core section (e.g., electrolyte) for systems, such as computer systems, cellular phones, etc. The battery cell also includes an internal circuit to monitor the state of the battery cell. The state that is monitored may include the temperature, charge level of the battery core section, the discharge/charge rate. The circuit may control the battery cell (e.g., cause charging of the battery cell). This internal circuit may be an integrated circuit, such as a microprocessor.

A lockout circuit is provided in a battery pack (10) which blocks charging by incompatible chargers while allowing charging by a compatible charger (12). The battery comprises a battery cell or cells (22), and a switch circuit (24). The switch circuit blocks charge current until a switch disable signal is provided to a switch disable contact (18). The switch circuit provides a one way bypass so that the battery may provide power to a device. To eliminate voltage drop while powering a device, a current sense circuit is provided to detect discharge current, and disable the switch circuit.

A battery heating device includes a temperature sensor and at least one heating element in a liquid and acid-proof arrangement inside the battery. The heating element is a power transistor secured to a cooling plate which is powered by the battery, the emitter of the power transistor being powered by a temperature control circuit when the battery temperature falls below a predetermined reference temperature and the battery voltage is higher than a lower threshold and lower than a higher threshold. A trigger circuit responds to a rise in battery voltage after the current in a load having a high current consumption is switched off. The trigger circuit actuates a timer circuit which conductively controls the power transistor for a set time if the battery voltage is under or at the lower threshold.