2. Scope of application of HVHF28 Series Defense DC-DC Converter

The high-reliability electronic system for aeronautics and astronautics, etc.
Table1 Product models

Single	Dual
HVHF28S5(F) HVHF28S12(F) HVHF28S15(F) HVHF28S8(F)	HVHF28D12(F) HVHF28D15(F)

3. Description of HVHF28 Series Defense DC DC Converter

The HVHF28 series products are designed using forward PWM principle and are new generation 20W series high-reliability DC/DC converter developed through improvement. After being isolated and coupled through optocoupler isolation, the sampling signal of output voltage of the product and the sampling signal of current in input circuit modulate the pulse width of controller at the same time. Its double-output close-loop control makes the product have stable voltage output and short-circuit protection function. Magnetic reset measures effectively prevent magnetic saturation of converter, thus improving the reliability of the product. In addition, the product also has fine adjustment function for output voltage.
These series products are made by the thick-film hybrid integration process and is totally sealed in a metal case. Both the design and manufacture of the product satisfy the requirements of GJB2438A-2002 “General specification for hybrid integrated circuits” and specific specifications of the products. The connection of input into HFG-CE03 power filter can improve EMC performance of the product.

4. Electrical performance (Table2, Table3, Table 4) of HVHF28 Series Defense DC to DC Converter

Table 2  Rated conditions and recommended operating conditions

Absolute max. rated value	Input voltage: 40V
	Output power: 20W
	Lead soldering temperature: 300℃/(10s)
	Storage temperature range: -55~125℃
	Inhibit voltage: ≤0.2V
Recommended operating conditions	Range of input voltage: 18~36V
	Case temperature(Tc): -55~＋125℃

5. Circuit block diagram (Fig. 2, Fig. 3) of HVHF28 Series Defense DC-DC Converter

Precautions for use:

• Upon power-on, be sure to correctly connect the positive and negative pole of the power supply to ensure correct power supply for fear of burning. When carrying out the electrical performance test, the test position shall be the pinouts of the product.
• Upon assembly, the bottom of the product shall fit to the circuit board closely so as to avoid damage of pins, and shockproof provision shall be added, if necessary.
• Do not bend the pinouts to prevent the insulator from breaking, which affects the sealing property.
• When the case temperature is 105℃, it is suggested that the thickness of heat sinking plate (copper) shall be 3mm, and the area shall be greater than 85mm x 50mm.
• When the case temperature is 125℃, it is suggested that the thickness of heat sinking plate (copper) shall be 3mm, and the area shall be greater than 80mm x 65mm.
• When the user places an order for the product, detailed electric performance indexes shall refer to the relevant enterprise standard.