Supertex inc. HV9922DB2 Offline, Non-Isolated, 23V, 45mA Auxiliary Power Supply General Description Specifications The HV9922DB2 is a universal input, offline, non-isolated Parameter Value auxiliary power supply using Supertexs HV9922 constant Input voltage: 85 - 265VAC, 50/60Hz current switching regulator IC. The output voltage is regulated to 23V +/-5% and is referenced to the negative Output voltage: 23V +/-5% side of the diode bridge rectifier (i.e. ground of the rectified Output current: 0 - 45mA DC voltage). The demoboard is protected against output Switching frequency: variable open circuit and short circuit conditions and meets FCC Class B (residential) EMI limits. 50% (at 110V input), Full load efficiency: 44% (at 220V input) The HV9922 acts as a constant 50mA current source which Open circuit voltage: 24V is sourced into an output zener diode. On the demoboard, a Output short circuit protection: Included 22V zener diode is used at D2 to regulate the output voltage to 23V within +/-5%. Lower output voltages can be obtained Dimensions: 53.4mm x 38.2mm by using an appropriate 2W zener diode in parallel to D2 in the space provided on the demoboard (D3). Board Layout and Connection Diagram + A + V 85 - 265VAC, 50/60Hz Connections: Input: Connect the input AC voltage between AC1 and AC2 WARNING: Do not use earth grounded test instruments or as shown. loads Doing so will short the AC line, resulting in damage to the instrument, load and/or the HV9922DB2. Use an iso- Output: Connect the output load between VO+ and VO- as lated supply or high voltage differential probes when testing shown. An ammeter and voltmeter can be connected as the circuit. shown to measure the output voltage and load current if desired. There is no galvanic isolation. Dangerous voltages are pres- ent when connected to the AC line. Doc. DSDB-HV9922DB2 Supertex inc. A032913 www.supertex.comHV9922DB2 Please note that at least 10V of total output voltage (drop Demoboard Testing: across the D2/D3 combination + drop across R1) is required Normal Operation: Power up the input voltage. Measure to ensure proper operation of the HV9922DB2. A lower volt- the output voltage and load current. The output voltage will age will not be sufficient to reset the inductor L1, and might be regulated to 23V +/- 5%. cause the inductor to go into saturation. Thus, if R1 is elimi- nated, the minimum zener diode that can be used in D3 is Note that, when left in this condition, the output voltage will a 10V zener diode. If lower output voltages like 5V are de- slowly drift. This drift is due to the power dissipation in the sired, R1 cannot be removed. zener diode, which causes the zener voltage to drift. This drift will eventually settle down once the temperature of the Typical Results zener diode stabilizes. This drift is not destructive and the output voltage will not increase more than 5%. Output Voltage Regulation: The regulation of the output voltage of the HV9922DB2 at various input voltages is shown To obtain an output voltage less than 22V, space is provided in Fig.1 (measured at full load of 45mA). Fig.2 shows the load on the HV9922DB2 for a zener diode (D3) in parallel with the regulation of the output voltage at 110VAC and 220VAC. existing 22V zener diode. By soldering in an appropriate 2W zener diode, the HV9922DB2 can be customized to produce Fig.1 Line Regulation of Output Voltage the required output voltage. 22.90 22.88 Line Regulation: Decrease the load resistance until the 22.86 load current reads the full load value of 45mA. Then, vary the input voltage between 85VAC and 265VAC and note the 22.84 output voltage. The output voltage of the HV9922DB2 will 22.82 remain in regulation over the entire line range. 22.80 90 140 190 240 Input Voltage (V) Load Regulation: Set the input voltage at a desired value. Vary the output load so that the load current is in between 0 and 45mA. The output voltage will remain in regulation over the entire load range. Short Circuit Test: With the HV9922DB2 operating in a Fig.2 Load Regulation of Output Voltage steady state, connect a jumper across the load (please note 24.2 that since there is no galvanic isolation on the demoboard, 24.0 this test should be done with care). Notice that the output 23.8 current rises to about 50mA and remains there. 23.6 23.4 23.2 The HV9922DB2 is protected against a short circuit by resis- tor R1 (200 ohm resistor). When the output of the demoboard 23.0 22.8 is shorted, the 50mA current develops a 10V drop across 01020304050 R1 to prevent loss of regulation. This voltage is sufficient to Output Current (mA) ensure that the inductor L1 does not go into saturation and 110Vac 110Vac thereby protects the circuit. However, this resistor dissipates about 0.5W of power during normal operation, causing a drop in the overall efficiency of the circuit. If short circuit pro- Efficiency: Figs.3 and 4 show the efficiency of the tection is not required, R1 can be eliminated. The difference HV9922DB2 at 110V input and 220V input respectively. The in efficiencies with and without R1 is shown in the Typical efficiency of the converter without the short circuit protection Results section. resistor is also plotted to show the effect of the resistor on efficiency. With the resistor removed, the full load efficiency increases by about 15% at 110V input and by about 11% at 220V input. Doc. DSDB-HV9922DB2 Supertex inc. A032913 2 www.supertex.com Output Voltage (V) Output Voltage (V)