This paper uses the Energy Star and Ecolabel standby criteria for reference, since ... are promoted around the world through well-known ecolabeling and energy ...
Energy saving potential and environmental impacts of televisions using energy-efficient power supplies Edson Adriano Vendrusculo1, José Antenor Pomilio2, Gilberto De Martino Jannuzzi3 1,2
School of Electrical and Computer Engineering, State University of Campinas, School of Mechanical Engineering, State University of Campinas, and International Energy Initiative Latin American Office –IEI-LA 3
Abstract This paper analyzes the standby power consumption of household televisions (TVs) and considers the new technologies available for switching-mode power supplies (SMPS). Semiconductor companies have introduced new, energy-efficient semiconductors, which have matured to the point of being currently available for SMPS applications. Further, these companies claim that 25% of total energy consumption is now consumed in the low power/sleep/standby modes. This analysis estimates the annual reduction in energy consumption and the CO2 conservation accruing from the reductions in natural gas power plant emissions that will result from the use of more energy-efficient TVs. It takes into account information about production, energy consumption, lifetime, and market share of TVs (assuming annual Brazilian sales of 20-inch TVs of 2,251,080 units in 2004 as estimated in a recent Brazilian government essay). Results indicate that at least one television is found in 87.7% of Brazilian homes. Throughout the country, household TVs consume 7.2 to 10.9 terawatt-hours (TWh) of electricity per year, or about 10–15% of Brazil’s residential electricity consumption. The overall consumption in 2002 was 72.7 TWh. This paper uses the Energy Star and Ecolabel standby criteria for reference, since regulations for establishment of standby power standards have not yet been passed by the Brazilian Congress.
I. Introduction In 2001, the Brazilian law 10.295/2001 set the principles for the “National Energy Conservation Policy and Rational Use of Energy”[1]. As long as this law is in place, all electric equipment commercialized in the country will be required to comply with Brazil’s energy efficiency regulations. Energy standards are promoted around the world through well-known ecolabeling and energy efficiency programs, such as Energy Star in the USA, the Ecolabel in Europe, and the Top Runner in Japan. In Brazil, the Procel labeling program has been continuously updated and revised following the worldwide trends. However, only recently, the Brazilian Congress decided to use the labeling program to establish standby power standards [2]. Since the Brazilian standards had not yet been established at the time of this research, this paper uses the North American and European standards for reference purposes. The main intent of this work is to assess the television (TV) sets available in the Brazilian market, based on the Energy Star and Ecolabel standards, which are the standby power criteria in the USA and Europe, shown in Table 1. Additionally, semiconductor companies have introduced technological improvements with impacts on energy efficiency. Some new semiconductor devices have matured to the point of being currently available for switching-mode power supply (SMPS) applications, which can increase the energy efficiency of TV sets. Finally, this paper summarizes the economic and environmental impacts of costeffective improvements in TVs, based on the reductions in energy consumption and CO2. It takes into account information about production, energy consumption, lifetime, and market share. In July 2005, Energy Star program celebrated the achievement of its first goal, i.e., the establishment of a 1-watt (1W) standby limit for TVs. As seen in Table 1, beginning in March 2005, advances in standby regulations in the European Community may yield even more strict limits on standby losses. Electronic improvements, however, may necessitate changes in the standby consumption regulations. In fact, the current standby definition may become inconsistent (see table note “a”) as a result of the establishment of new operating modes, such as “sleep” and “deep sleep.” A worldwide agreement for household appliances operating on standby mode has been discussed on numerous occasions; a low
power mode (LOPOMO) designation, which is under discussion, is outlined on the standby power home page of Lawrence Berkeley National Laboratory [6]. TABLE 1. Energy-Efficiency Specifications for Qualified TVs ENERGY STAR (USA)[4] ECOLABEL(Europe) [5] a (standby mode ) Product Phase I Phase II Phase III Effective from 1 April 2002 until 31 March 2005. (effective (effective (effective 7/1/02) 7/1/04) 7/1/05) b < 1W (for passive standby consumption ≤ 1W (analog) c and < 9W (for active standby consumption of TV and ≤ 1W ≤ 3W the televisions which have an integrated digital ≤ 3W (digital) receiver/decoder) a Standby power is defined as the power being used when the product is connected to a power source, produces neither sound nor picture, does not transmit nor receive program information and/or data (excluding data transmitted to change the unit’s condition from “standby mode” to “active mode”), and is waiting to be switched to “on” (active/play mode) by a direct or indirect signal from the consumer, e.g., with the remote control [1]. b Passive standby – the television is connected to a power source, produces neither sound nor picture, and is waiting to be switched into an “off”, “active standby,” or “on” mode, on receipt of a direct or indirect signal, e.g. from the remote control [2]. c Active standby – the TV is connected to a power source, produces neither sound nor vision, and is exchanging/receiving data with/from an external source [2]
II. Test Criteria The specifications that products must meet to get an energy-efficiency endorsement in different regions depend on the local electrical distribution system and other circumstances. For Energy Star labeling, only the consumption in the standby mode is considered, whereas the European Ecolabel 1 regulations also take into account the consumption in “on mode.” . Energy Star specifies general criteria for voltage and total harmonic distortion (THD) lower than 3% and ambient temperature in the range of 22°C ± 4°C. The nominal voltage is a market-specific criterion; the recommended values are listed in Table 2. TABLE 2. Market-Specific Criteria for Energy Star Market: United States Europe and Australia 115 VRMS ± 3 VRMS 230 VRMS ± 10 VRMS Voltage Frequency
60 Hz ± 3 Hz
50 Hz ± 3 Hz
Japan 100 VRMS ± 5 VRMS & 200 VRMS ± 10 VRMS 50 Hz ± 3 Hz & 60 Hz ± 3 Hz
Ecolabel regulations use the technical standard EN 50301 [7] to measure power consumption of appliances and equipment during normal operation (“on mode”). In addition, Working Group 9 of the International Electrotechnical Commission (IEC) Technical Committee TC59 prepared the international standard IEC 62301, i.e. “Household Electrical Appliances – Measurement of Standby Power”[8]. Progressively more energy-efficient standby power devices have been offered by semiconductor manufacturers since the Energy Star, Blue Angel, and Top Runner programs released their energy efficiency specifications for power supplies used in consumer electronics products. To highlight these manufacturers’ efforts, the following section discusses the energy losses in a very common topology for SMPS.
III. Reduction of standby losses in Switching-Mode Power Supply Semiconductor manufacturers claim that 25% of total energy is consumed in low power/sleep/standby mode and around 75% of average total energy consumption is in active mode. Further, in active mode, changing semiconductor efficiency from 60% to 75% can result in 15% energy savings [13].
1 “On mode” - the television is connected to a power source, and produces sound and vision.
Consequently, much analysis is being done on the losses in standby and active mode (see example in Figure 1 for flyback topology), on driving TV sets and other audio devices [13].
Cout
Rstartup Resr
rede mains
Error and Erro biasing
Resout Crss
Cbulk
Controlador controller
Coss
Cgs
Standby Mode 1.Capacitive losses: 1 .C.V 2 . f sw 2 2. Biasing network 3.Controller current 4.Gate charge: Q g . f sw
Active Mode 1.Rectifier conduction 2. Transformer core and copper losses 3.FET conduction losses 4.Resistor dissipative loss 5. Snubber losses
5. Start-up network Figure 1. SMPS common topology: losses in standby mode There are several key sections of the SMPS that can be optimised to minimise standby power consumption. The losses can be categorised into two types – conduction losses and switching losses [19]. Power switches based on MOSFET (Metal-oxide-semiconductor field effect transistor) technology devices have a named on-state resistance, Rds(on), which represents a major area of conduction loss. This loss can be minimised by selecting MOSFETs with lower Rds(on). Unfortunately, these devices tend to have a larger gate capacitance, which in turn increases the switching losses. However, depending on the output power rating, it is possible to select a MOSFET that strikes an appropriate balance between switching and conduction losses. Power input (Pin)—see equation (1)— helps provide a comprehensive insight into SMPS losses with regard to both aforementioned strategies. It is deduced considering that, in a switching period, the energy drawn by the transformer during the on-time is transferred to the output during the off-time. As a result:
1 2 Pin = × L p × I pk × f sw 2
(1)
where Lp is the transformer primary inductance, Ipk is the inductor peak current, and fsw is the normal working switching frequency. Two strategies, both linked to the SMPS switching frequency, have been established to reduce losses. By employing burst-mode operation (the so-called “skip-cycle” mode) or decreasing the switching frequency as much as possible, one may achieve a reduction in the switching losses in standby mode. These strategies are described below. a) Burst-mode operation or skip-cycle mode Especially when the requirement to provide output power is minimised, it is possible to operate the power supply in “bursts”, whereby the output power is supplied in small periodic bursts of pulse width modulated (PWM) operation, rather than in continuous mode. This minimises both conduction and switching losses. While this feature has been employed in high-end designs, it has only recently been needed in power supply designs for output power under 100 W. In this mode, switching cycles are automatically skipped when the output power demand drops below a given level. This is usually accomplished by monitoring a feedback pin available in controllers. When the controller enters the controlled-burst operation, the power transfer depends on the width of the pulse bunches, as seen in Figure 2 for P1
