MHP-Series-AN (4C).qxd 4/2/04 4:37 PM Page 3 Resistive Components Model MHP Non-Inductive Planar Thick Film Power Resistor 20 Watt, TO220 Package A subsidiary of TT electronics plc Applications • Switching power supplies • Snubbers • In-rush / bleeder resistors • Current limiters Features • High power density • Power is dissipated above circuit board • Low thermal resistance • Non-flammable • Non-Inductive planar BI Technologies MHP-Series-AN (4C).qxd 2 4/2/04 4:28 PM Page 4 BI Technologies Electrical Resistance Range, Ohms 0.01Ω to 100K Resistance Tolerances Standard 5%, Optional 1% & 2% Operating Temperature Range -55°C to +155°C Temperature Coefficient of Resistance, Maximum ** 100ppm/°C Power Ratings * 20 Watts Operating Voltage, Maximum 500V 15 x rated current up to 8ms ∆(R±0.5%) Peak Current Dielectric Strength 1500V * Power rating at 25°C case temperature. Power rating without a heat sink is 2.25 watts at 25°C ** Consult factory for values below 0.1 Ohm Standard Resistance Values (Ohms) Value - Ohms 0.01 0.1 1 5 10 20 50 100 200 1K 2K 10K 20K 50K 100K Code 0R01 0R1 1R0 5R0 100 200 500 101 201 102 202 103 203 503 104 Mechanical Lead Material Tin Plated Copper Alloy Substrate Material 96% Alumina Resistor Material Environmental Thick Film (Per MIL-PRF-83401) Thermal Shock Max ∆R ± 0.50% Terminal Strength Max ∆R ± 0.25% Short Time Overload 2 x rated Power for 5 Seconds Max ∆R ± 0.50% Moisture Resistance Max ∆R ± 0.50% Mechanical Shock Vibration Shock 30 G’s, ∆R ± 0.25% 10G’s, 10 to 500 Hz ∆R ± 0.25% Low Temperature Storage Max ∆R ± 0.25% High Temperature Exposure Max ∆R ± 0.25% Load Life 1,000 Hours Max ∆R ± 2.00% Resistance to Solder Heat Max ∆R ± 0.25% Dielectric Withstanding Voltage, Minimum 1500V Marking Permanency MIL-STD-202, Method 215 Lead Solderability MIL-STD-202, Method 208 Flammability Storage • Specifications subject to change without notice. • Contact factory for custom products, non standard values and tolerances. UL 94V-0 Rated -55°C to +155°C MHP-Series-AN (4C).qxd 4/2/04 4:28 PM Page 5 Resistive Components Outline Dimensions (mm) 10.54 Max 1.27±.13 2.75±.13 Mould Angle 5˚±2˚ Typical 6.24±.30 14.99 Max 3.84±.13 6.17 Ref 14.22 Max Marking this surface 0.47±.10 2.61±.32 4.45±.39 1.33±.19 0.83±.20 5.08±.25 Dimensions are in millimetres Substrate Material: 96% Alumina Lead Material: Copper Alloy, Tin Plated Resistor Material: Thick Film Power Derating Curve Ordering Information MHP Percent of Rated Power 100 20 103 J Model Power Rating 80 Resistance Code 10 mOhms : 0R01 100 mOhms : 0R1 1 Ohm : 1R0 5 Ohms : 5R0 10 Ohms and above First 2 digits are significant. Last digit denotes number of trailing zeros. 60 40 20 0 25°C 155°C Temperature Packaging 50 per Tube • Specifications subject to change without notice. • Contact factory for custom products, non standard values and tolerances. Tolerance Code J = 5% Tol G = 2% Tol F = 1% Tol 3 MHP-Series-AN (4C).qxd 4/2/04 4:28 PM Page 6 Resistive Components 1. Inrush Current limiting The PFC circuit generates a regulated DC output while controlling the input power factor. The input current is sinusoidal and in-phase with the mains voltage. Due to the large bulk capacitors at the PFC converter output a substantial inrush current can be drawn at power-up. The magnitude of the inrush current depends upon the instance of the AC waveform at which the unit is turned on. Inserting a current limiting resistor in series with the mains supply will control start-up inrush current. The resistor is short-circuited by using a relay once the bulk capacitor is charged. D5 Normally open relay S1 D1 Fuse VDC L1 D3 R2 L Inrush limiting Resistor PFC Drive MHP Bulk Capacitor Q1 N D2 D4 0V Inrush current limiting 2. Regenerative Power Dissipation A stepper motor will act like a generator if the shaft is mechanically rotated. Thus inertia energy supplied to the motor during acceleration is returned to the drive during deceleration. This is regeneration and increases the motor current, which could damage the power switches. A current threshold detector in the circuit detects the increased current and momentarily turns off the switches. The regenerated current now has a path back to the supply and charges the bulk capacitor to a higher voltage. Since the power switches have been turned off the current in the threshold detector falls below the threshold and the power switches are turned on again. If the current remains higher than the threshold the drive returns to the regenerative state. If the power supply capacitor voltage increases to a high enough level then the power switches may be damaged. To avoid this regenerative power dissipation circuit can be used. A reference voltage equal to the incoming AC is developed across C1 and under normal conditions will equal the drive circuits bulk capacitor voltage. During regeneration when the bulk capacitor voltage rises above the incoming AC peak the regenerative power dissipation circuit transistor will turn on connecting a power resistor across the bulk capacitor. When this voltage has decreased to the AC peak value the transistor will turn off. The instantaneous regenerative current will be high but the average power dissipation in the resistor will be low due to the short regeneration period. The value and power rating of the power resistor will depend upon the regeneration energy, bulk capacitor value and AC voltage. One or more MHP resistors may be used and the regenerative power dissipation may be considered a temporary overload provided the regenerative energy is dissipated is less than 5 seconds. D3 D1 MOTOR Q3 Q1 Power Dissipation Circuit Power Supply Output Capacitor D2 D4 Q4 Q2 Rsense Stepper motor drive circuit Power Resistor D2 D1 R5 MHP TR1 VAC 1K R2 100K R3 C1 R6 TR2 R4 0V Regenerative power dissipation circuit 3. Current Sensing Non-inductive resistors are suitable for current sensing applications. When switching at high frequencies stray inductance can cause ringing with parasitic capacitances. This may cause the over current sensing to shutdown the power switch prematurely limiting the output power. Even with the correct choice of resistor care must be taken to keep the component leads and PCB traces short to minimize inductance. A buck converter lead acid battery charging application using a current sense resistor is shown opposite. VBATT D1 VIN Q1 L1 Battery D2 C2 Rsense COM MHP Control IC VFB CS CS+ Switchmode lead acid battery charger + 4 MHP-Series-AN (4C).qxd 4/2/04 4:23 PM Page 1 Resistive Components 4. Snubber Circuits The low inductive properties of the MHP power resistors make them ideal for high frequency snubbing applications. This example shows a flyback converter with snubbing circuits on the primary switch and output diodes. Leakage inductances in the circuit are unclamped and responsible for voltage spikes at the drain of the power switch as well as the secondary output diodes during the switching transitions. The RC snubber network dampens circuit resonance, caused by component parasitics; this limits the voltage stress on the devices, improves circuit efficiency and reduces radiated EMI. RC snubber circuit components that have extremely low parasitic inductance should be chosen to avoid unwanted resonance in the circuit. Ceramic capacitors are available with low ESR and ESL values. Wire wound resistors often have too much inductance and will cause ringing and voltage overshoots. VIN MHP RC Snubber VOUT MHP Vref RC Snubber Vout VOUT Vfb RC Snubber MHP Flyback converter with RC snubbers 5. Capacitor Discharge An important aspect in power supply design is the provision of a quick safe discharge of the bulk capacitors at turn off. The electrolytic capacitors can hold large charges, which if left to self-discharge allow dangerous voltages to remain for long periods of time presenting potential safety hazards for service personnel. The discharge of 0.25J of stored energy to the human body can provide a heavy shock and 10J can be fatal. Thus a discharge resistor is required. The energy stored by the input capacitors is equal to 2 1/2CV where V is the PFC output voltage. The discharge resistor must be chosen to provide a quick discharge to a safe voltage when the unit is -t/ turned off. Using V = Vse , the RC time constant is calculated. If the resistor continuously dissipated power it would represent an unacceptably high loss. It is only switched into the circuit when needed therefore reducing the required resistor power rating. The capacitor discharge may be considered a temporary overload condition. D5 VDC L1 Discharge Resistor D3 D1 MHP L PFC Drive Bulk Capacitor Q1 N S1 D2 D4 Normally closed relay 0V Capacitor discharge circuit 6. Audio Crossover Circuits Loud speakers are optimised to reproduce sound within specific frequency bands. A crossover circuit in the speaker system splits the audio signal into multiple signals. So the signal going to the bass (or woofer) has just the low frequencies in it. The signal to the mid-range has the middle frequencies, and the signal to the tweeter has the high frequencies. The goal of the audio system is to generate an accurate response to the input signal over the complete audio spectrum however the frequency response of the individual speakers is not always flat through the crossover region. Thus a compensation network is required to correct for the impedance variations of the speakers. Non-inductive resistors are suitable for this application. Crossover + Compensation MHP Tweeter Comp Resistor Comp Resistor MHP - 40dB/Decade passive crossover circuit Woofer 5 MHP-Series-AN (4C).qxd 6 4/2/04 4:23 PM Page 2 Resistive Components BI Technologies - SMT BI Technologies - ECD BI Technologies - MCD Company Profile Company Profile Company Profile BI Technologies, SMT Division is a World Class manufacturer of thick film Passive Components. The company was established in 1958 in Glenrothes, Scotland. BI Technologies have earned a great reputation as a high quality, high volume, cost effective and responsive supplier of thick film passive components for telecommunications, computer, automotive, medical and industrial applications. BI Technologies has been an innovator and leader in electronic components for more than 50 years manufacturing products for communication, computer, industrial and automotive applications. BI Technologies, Magnetic Component Division, headquartered in Fullerton, California, with a manufacturing base in Kuantan, Malaysia, is a world leader in miniature surface mount high power inductors. The magnetic material and manufacturing expertise of various inductors, choke coils, transformers and assemblies has expanded the customer and market base into automotive, medical, computer, data communication and industrial in addition to other specialized magnetic assembly applications. Product Range Product Range Product Range • Packaged SIL, DIL and Surface Mount Resistor Networks • Chip Resistor Arrays • Chip Resistor - Capacitor Arrays • Planar Power Resistors • Surge Resistors • Thick Film Substrates • Custom Thick Film products • High Voltage Resistors and Networks • Trimming and Precision Potentiometers • Position Sensors • Chip Resistor Arrays • Resistor Networks • Integrated Passive Networks • Inductors • Transformers • Turns Counting Dials • Hybrid Microelectronics and Custom Integration Products • Transformers both surface mount and through hole • Surface Mount high powered inductors • Toroidal inductors (through hole and surface mount) • High power specialty laminate transformers • Data communication modules, filters, and transformers for ethernet and DSL • Common mode filters and chokes • Planar transformer solutions BI Technologies serves a global customer base with manufacturing locations in the United States, Mexico, Scotland, Japan, China and Malaysia. BI Technologies SMT BI Technologies ECD BI Technologies Pte Ltd TT electronics GmbH Telford Road, Glenrothes Fife KY7 4NX, Scotland, UK 4200 Bonita Place Fullerton, CA 92835, USA Max-Lehner-Strasse 31 85354 Freising, GERMANY Tel: +44 1592 662200 Fax: +44 1592 662299 [email protected] Tel: +714 447 2300 Fax: +714 447 2400 [email protected] 514 Chai Chee Lane, #02-01 Bedok Industrial Estate 469029 SINGAPORE TT electronics SA TT electronics S.r.l. 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